The present invention relates generally to devices for the rehabilitation of injuries, and particularly to an improved inflatable boot for wearing by an individual to promote healing of an injured foot, ankle or lower leg area. An inflatable boot is a therapeutic device worn on an injured foot and ankle to encase and massage the injured area, and to create an increase and decrease of pressure within the muscles of the foot and lower leg to simulate the pressure changes normally experienced during walking. These pressure changes are important to the flow of blood through the foot and lower leg. My earlier U.S. Pat. No. 4,805,601, incorporated herein by reference, discusses one such inflatable boot. The present device offers many advantages over my earlier device, such as being easier to manufacture and use.
The increase and decrease of pressure within the muscles of the foot and lower leg improves blood flow by acting as the driving force of a naturally occurring pump within the foot and lower leg. The veins of the foot and lower leg contain one-way check valves. When the pressure in the muscles and tissues surrounding the veins is increased, blood is forced out of the veins toward the heart, and when the pressure decreases, fresh blood is allowed to flow into the veins. Repeated increases and decreases of pressure, such as when walking, therefore operate to pump blood through the foot and lower leg. This pumping action is particularly important for the return of blood to the heart from the foot and lower leg because these portions of the human body are a long way from the heart.
When a foot is injured, it often is painful and harmful to put weight or the foot, or even to flex the muscles of the foot. It therefore is very difficult to maintain a proper flow of blood through the injured foot. A proper flow of blood is helpful to recovery of the injured area because blood is essential to the functioning of the cells in the body.
It has been found that one safe way to improve the flow of blood within an injured foot is to encase the foot and injured area in an inflatable bladder, as described briefly above. The pressure within the bladder then is increased and decreased to result in an increase and decrease of pressure on the tissues of the foot. A pressure change within the bladder may be controlled by a pump and valve attached to the bladder, or by pressing on and releasing the exterior of the bladder.
A simple way of pressing on the exterior of a bladder is for the wearer of the bladder to press the bladder against a wall, floor, bed frame, or other obstacle. The boot shape of the bladder of the present invention includes a sole portion corresponding to the sole of an encased foot, and allows a pressure change to be controlled by pressing on and releasing the sole portion of the foot. This is a movement that is particularly easy for an injured wearer of the boot to make, because it takes advantage of the large muscles of the leg that are used for walking. The sole portion of the bladder is fluidically interconnected to a leg portion, by which it is meant that a pressure change in fluid within the sole portion effects an immediate, corresponding pressure change in fluid within the leg portion. In this manner, an injury located anywhere within the area encompassed by the boot may be operated upon by a pressure change in the boot, and may receive fill benefit of the pumping action described.
Inflatable boots are used to treat various types of injuries, including bruises, sprains, fractures, torn muscles, and injured tendons. For most of these injuries, the orientation of the injured foot within the boot is very important. The boot must protect the injured foot and lower leg, prevent excessive motion of the foot about the ankle, and include a sole portion that is of a sufficient volume so that pressing on the sole portion produces a desirable increase in pressure within the bladder surrounding the foot, preferably from approximately 1-psi to 2-psi.
An inflatable boot provides protection by maintaining a cushion of slightly pressurized air around the foot and lower leg, at a pressure of approximately 1-psi when the boot is in its relaxed condition. A thick cushion usually provides better protection than a thin one. The pressure within the cushion tends to force the walls of the cushion into a stable configuration, at least partially immobilizing the foot to limit motion about the ankle. A thick cushion within the sole portion of the boot also means that the sole portion is of a relatively large volume, allowing a substantial increase of pressure within the sole portion with a simple pressing force applied to the sole portion. For the preferred embodiment, the pressure within the boot may be increased from 1-psi when relaxed to 2-psi when a pressing force is applied to the sole portion. If adequate interconnection is provided between the sole portion and the rest of the boot, an increase of pressure in the sole portion results in the desired increase in pressure within the entire bladder of the boot.
The importance of each of these factors varies depending on the condition of the wearer of the boot. For a relatively immobilized wearer, such as someone suffering from injuries in addition to those of the foot, none of the factors is particularly important. The foot will not be subjected to many dangers that would require protection and support, and the boot may be used with an external pressure source like a pump. As the wearer becomes more mobile, protection and support become more important, and utilization of the self-powered method of pressure increase becomes more viable.
After careful study of all of the issues identified above, I have found that the effectiveness of an inflatable boot is a function of how accurately the boot may be placed on the foot, how thick of an air cushion is provided around the foot for protection, how positively the sole of the foot may be located on a fluid-filled platform within the boot, and how effectively pressure is transmitted from a sole portion of the boot underlying the sole of the foot to wall portions, surrounding the ankle and lower leg. The present invention includes elements that satisfy each of these design parameters. The preferred embodiment includes both visual and tactile indicators of the proper placement of the boot, in the form of notches near a heel region of the boot corresponding generally to the bottom of the heel of the foot, regions of noninflation near the sole portion of the boot generally along lines that correspond to the proper placement of the sole of the foot, and a partially enclosed toe region that corresponds generally to the proper placement of the top of the toes of the foot. It also includes a structure that causes the boot to form a foot-supporting platform under the sole of the foot when the boot is inflated. The structure also defines a sole portion and connected wall portions with fluid transfer between the sole portion and the wall portions being facilitated by a relatively unobstructed interior. Alternatively, a sling may be suspended within the boot to provide a platform for both locating and supporting the foot. The construction of the preferred and alternative embodiments is relatively simple, allowing the production of a cost-effective therapeutic device.
The inflatable boot of my earlier patent fulfilled all of the design requirements identified above, but only because the boot of my earlier patent is a relatively complicated structure, with separately defined sole and wall portions interconnected by a series of openings or apertures. A resulting drawback of that structure is that it is difficult to manufacture, and therefore relatively expensive. This drawback is solved by the novel construction of the present invention.
In addition to my earlier patent, several other patents show examples of inflatable boots. For example, U.S. Pat. Nos. 3,083,708 and 3,403,673, incorporated herein by reference, each show what is believed to be an inflatable boot formed with one or two chambers that have a substantially unobstructed interior. The boots disclosed in U.S. Pat. Nos. 3,083,708 and 3,403,673 also appear to be relatively simple in construction, and therefore easy to manufacture.
However, each of these two devices is formed with a seam that extends along the center of the sole portion of the boot, creating a valley that may limit the volume of the sole portion when inflated. This may limit the effective increase in pressure that is affected by pressing on the sole portion. The boot of my present invention may be made from a folded-over bladder that eliminates the center seam of these prior devices, as described in more detail below. The other benefits of my invention, as described herein, may be used with boots that include such a center seam, and these alternative constructions of boots are intended to be encompassed within the spirit and scope of the invention defined in some of the appended claims.
More complicated inflatable boots are found in U.S. Pat. Nos. 3,824,992, and 3,888,242, also incorporated herein by reference. As with the above-discussed patents, these boots are manufactured with what appears to be a single bladder having a relatively unobstructed interior. The '992 device includes a relatively stiff outer cover, and the '242 device includes numerous seams and overlapping flaps. Both of these features may complicate manufacture and use of inflatable boots, but may be used as part of alternative embodiments also within the spirit and scope of the invention defined in the appended claims.
The treatment of foot and lower leg injuries may involve the application of cold or heat to the injured area, such as by placing an ice pack or a heat pack on the injured area. Ice packs and heat packs are examples of what are referred to more broadly herein as thermal treatment devices. Proper placement of thermal treatment devices is very important, and often very difficult, because of the numerous possible locations of the varied injuries for which inflatable boots are used.
For many foot injuries, the application of a thermal treatment device under slight pressure, such as the 1- to 2-psi found within an inflatable boot, may be beneficial because it increases the thermal transfer rate between the treatment device and the injured area to be treated. The increase and decrease of pressure provided by proper use of an inflatable boot also helps to reduce the discomfort of a treatment device pressing against the foot, and to maintain the blood flow that otherwise would be restricted further by the treatment device. The preferred embodiment of the present invention includes a pocket formed on the inner, foot-contacting portion of the boot that aids in proper placement of a thermal treatment device on the foot, and allows the beneficial increases and decreases of pressure on the foot to be transmitted through the treatment device.
It is a general object of the present invention to provide an inflatable boot that is easy to manufacture and simple to use.
It is another object of the invention to provide an inflatable boot with a bladder, and with a structural interconnection joining an inner layer of the bladder to an outer layer of the bladder to create a foot-supporting contour when the bladder is inflated.
A still further object of the invention is to provide an inflatable boot with a visual reference indicating the proper placement of a heel of a human foot, prior to inflating the boot, so that an inflated cushion may form properly under the sole of the foot when the boot is inflated.
It is an additional object of the invention to provide an inflatable boot with a platform-defining sling so that the sling may support a human foot that is inserted into the boot.
A still further object of the invention is to provide an inflatable boot with a pocket in which a thermal treatment device may be held.
These and additional objects and advantages of the present invention will be understood more readily after a consideration of the drawings and the detailed description of the preferred embodiment.